This invention relates to a billing method in a telecommunications system. The invention relates more specifically, but not exclusively, to a billing method which can be carried out with an identification card, as well as to an identification card.
In telecommunications networks, for example in telecommunications networks based on the GSM standard, the amount charged for a call depends upon various parameters, in particular the time of day, and, among other things, the geographic location of the calling and the called subscriber. These parameters, in particular the duration of the call, are established in the infrastructure of the network, for example in a central control office. The amount to be charged is then determined on the basis of these parameters, and is debited against an account of the subscriber at the network operator or at a financial institution. This billing method is extremely time-consuming and expensive for the network operator, and requires a complex billing system and many manual or semi-automatic operations.
In addition to this post-paid billing method, prepaid systems are also known. Prepaid systems usually use a subscriber-specific identification card, including an account which can be loaded with a monetary amount. The amounts billed for calls of the subscriber are then debited from this account after each call. Various methods are known by which money can be loaded again onto the account. The parameters needed to determine the amounts billed are known by the term CAI (Charge Advice Information), and are established in a server administered by the network operator, and are transmitted to the identification card of the subscriber with signalling messages. Processing means in the card then indicate the amount billed on the display of the mobile device in the local currency, and debit this amount from the stored monetary amount.
Described in the patent application WO 95/28062 are a method and a SIM card for carrying out a prepaid system. According to the disclosed teaching of WO 95/28062, so-called charge advice information ("e"-parameters) according to the GSM standard are transmitted to a respective mobile device, and are further transmitted to the SIM card when a call is established by the mobile device, which card checks whether the stored prepaid amount is sufficient for the incoming or outgoing call. If the amount is sufficient, the procedures for establishing the call are concluded, according to WO 95/28062, and a timer of the SIM card (or of the mobile device) is started to measure the duration of the call. According to WO 95/28062, the call costs are determined from the measured duration of the call as well as based on tariff information, which is stored in the SIM card or which is transmitted to the mobile device via the network by means of further charge advice information, and the costs are deducted from the prepaid amount. According to WO 95/28062, special charge advice information can be transmitted periodically to the mobile device over the network while the call is established, which charge advice information is acknowledged by the SIM card if the prepaid amount still suffices to continue the call.
Prepaid billing methods are inexpensive for the network operator, who does not have to write any invoice. He still has to carry out the evaluation of the amounts to be charged, however. Moreover this method can be applied in the GSM sphere only with devices and in geographic locations where the Advice of Charge (AOC) function, defined in standard ETSI ETS300 510 (corresponding to the technical specification GSM 02.24), can be applied. Therefore prepaid cards usually allow only very limited roaming possibilities.
Prepaid methods are also known in connection with intelligent network (IN) solutions. These methods are expensive to use, however, and can only be applied in the network of the respective operator.
Described in the patent application WO 96/11545 is a smart card comprising a clock and a calendar, both of which are connected to a microprocessor which, for its part, is connected to a memory. According to the teaching disclosed in WO 96/11545, this smart card is inserted in a subscriber unit, and a subscriber identity as well as a period of validity, during which the subscriber unit is to use the subscriber identity and the smart card can no longer be used, are communicated to the subscriber unit.
Described in the patent application EP 0 724 371 A is a method by means of which a wireless communication terminal can select the preferred network from among at least two wireless networks, the least expensive network typically being selected based on network tariff information which is stored in a centralized server environment.